The problem is the extra day of the conference

The problem is the extra day of the conference.
We have a one-day conference.
In the “Site Management”> “Conference Schedule” the end date of the conference is forced to +1 from the date of the start of the conference.
As a result, instead of a one-day conference, it turns out to be a two-day one.
The adjustment of this date is not saved: I specify August 16, save, re-open the schedule management - and there on August 17.

To make the system accept the correct date, I spend a cycle of adjustments in the end date of the conference:
I specify the end date 08/16/2020 (at the same time I have to correct and the archiving date)> save> open settings again and change year 2020 → 2019> save. The result is a one-day conference.

But the next time you open the conference schedule settings page, the end date is again August 17, 2019.

How to fix the situation.